1. Field
The following description relates to a terahertz continuous wave emitting device, for example, to a terahertz continuous wave emitting device wherein an absorption area is formed between a plurality of light sources in a ‘configuration having a photo diode that is operable at high speed’, and wherein an antenna is integrated into the absorption area, whereby the terahertz continuous wave emitting device can be manufactured in a single device.
2. Description of Related Art
Due to new characteristics of a terahertz (THz) wave having a frequency of 0.1 THz˜10 THz and thus being harmless to humans due to its low energy, and numerous molecules having a unique spectrum in this band, much research is being conducted on terahertz continuous waves.
Time-domain spectroscopy (TDS) systems using femtosecond (fs) lasers have been mainly used in researches so far. TDS system is a method of exciting a carrier in a photoconductive switch using femtosecond lasers. Herein, the photoconductive switch is made of a material having a very short carrier lifetime, and thus, using this material, the photoconductive switch plays a role of enabling a femtosecond grade pulsed shape current to flow. Therefore, by such a photoconductive switch, a pulsed shape current would flow in an integrated antenna, generating broadband terahertz waves that are to be spread in the air. Ultimately, TDS system is basically a method using pulsed shape THz waves.
However, a disadvantage of fs-lasers is that they are too big and expensive. Not only that, for applications used in industrial fields, small and portable systems that could obtain results from frequency bands that use THz continuous waves (CW THz) rather than time domain spectroscopy are more useful.
For this reason, photomixing method that uses a photomixer and lasers having two different frequencies is being studied for field application and realization of subminiature systems.
Photomixing is basically a method of using a beating light made from two different laser lights. More specifically, photomixing is a method of generating a beating light of a terahertz frequency with laser lights of two different frequencies, generating an alternating current of a terahertz frequency in a photomixer using the generated beating light, and enabling the antenna integrated in the photomixer to emit terahertz waves. The frequency of the terahertz waves generated by such a photomixing method is the same as the frequency of the beating light, and consequently the same as the wavelength difference between the two lasers. Therefore, according to this photomixing method, it is possible to adjust one of the two laser wavelengths and make a Terahertz wave emitter capable of frequency tuning.
Meanwhile, terahertz continuous wave (CW THz) emitting systems that are currently being sold for industrial uses are configured to use two independent lasers and one independent photomixer. More specifically, as in FIG. 1, a terahertz continuous wave emitting system is configured such that two independent lasers having different frequencies generate a beating light of a terahertz frequency, and then the generated beating light is irradiated upon an ‘independent photomixer’.
However, there is a problem that in such a terahertz continuous wave emitting system, the beating light generated by two independent lasers leak outside the device and is then irradiated upon an independently configured photomixer, and thus light loss may occur in the process. Furthermore, since such a terahertz continuous wave emitting system is embodied to comprise a plurality of independent devices(two independent lasers, and one photomixer independent from the two independent lasers), there is a problem of limitation to simplifying the structure of the system.
Therefore, there is a need for a new technology of emitting terahertz continuous waves that can be differentiated from such an terahertz continuous wave emitting system aforementioned.